More than 20 years after its run as a groundbreaking DC Comics series ended, Watchmen was adapted for the big screen by Zack Snyder and released as a major motion picture on March 6, 2009.

For its soundtrack, the creative team didn't have to look far. Music was referenced throughout the graphic novel, so some of the songs, including classics by Bob Dylan and Jimi Hendrix, made their way into the movie.

The film takes place in an alternate 1985, where a group of superheroes known as the Minutemen, later replaced by the Watchmen, had been affecting U.S. history since the late '30s, both for better (winning the Vietnam War) and worse (preventing Watergate from happening, with Richard Nixon continuing to win re-election after re-election).

By the '70s, a backlash against superheroes results in legislation outlawing them, with most of them being forced into retirement. But with society on the brink of collapse and a potential nuclear war with the Soviet Union looming, the Watchmen reunite in order to save the planet.

Dylan's "The Times They Are A-Changin'" plays over the title sequence, which shows the heroes changing society over 45 years. As Snyder explained, the idea to use the song came early.

Watch Bob Dylan's 'The Times They Are a-Changin'' From 'Watchmen'

"From the very beginning I wanted to do a cool title sequence for the movie, and it was actually the thing that got me started drawing Watchmen because they were trying to figure out how much this movie was going to cost," he told Animation World Network at the time.

"And I said it's really impossible to say until I start drawing the movie and get a sense of what the movie is. ... So, I said, 'Look, to get a handle on some of the things, maybe I'll draw the title sequence so we can see how much that is.' But I literally went to the beginning of the movie and started drawing. It was funny because I had the music -- I was pretty positive that it was going to be Bob Dylan's 'The Times They Are A-Changin'.' And then it started to take shape for me as we really find out where we are in the world, and that's how that sequence came about, tracing the alternate history. There's a bunch that I shot that we didn't use because it got too long like the Comedian raising the flag on Iwo Jima by himself and Nixon being sworn in."

Another Dylan song, "Desolation Row," plays over the closing credits, albeit in a version covered by My Chemical Romance that was recorded specifically for the movie. Their take owed a stylistic debt to the underground punk rock of the era in which the movie is set.

“We were on the Project Revolution [Tour], and I got a call on my phone," MCR frontman Gerard Way said. "Somebody had put Zack through to me, and he was immediately excited. And so we started talking [about the song], and he said, ‘Well, what are you thinking?’ Because originally he said, ‘Let’s just have a 10-minute version that goes through the whole credits.’ And I was originally cool with it."

But Way noted that "since the story takes place in an alternate early ’80s, I wanted to make the song a product of that era. And there’s a lot of gangs in Watchmen, there’s a couple bands [mentioned], like Pale Horse, and you never know what those bands sound like, but I’m assuming it sounds like early ’80s punk or late-’70s punk. … And he said, ‘That sounds perfect.’”

And because the story spans decades, songs by Nat King Cole ("Unforgettable") and Billie Holiday ("You're My Thrill") are also incorporated. So is KC and the Sunshine Band's disco smash "I'm Your Boogie Man," and Wagner's "Ride of the Valkyries," famously used in Apocalypse Now, gets another setting during the Vietnam War, where Dr. Manhattan helps the U.S. win the conflict.

As Tyler Bates, who composed the similarly eclectic score, said, Snyder's use of music in Watchmen helps sell the idea that what you're seeing on the screen is real and not part of an alternate universe.

"With Zack's movies there's always a pulp element," he told IGN. "If you look at the story of Watchmen, it's definitely a skewed or distorted expression of the '80s in a large part -- the pop culture of the '80s is fused into it, especially when you look at the song list. Somehow '99 Luftballoons' is in the movie. The one thing about Zack's movies is that there is usually all this insanity that takes place and yet there's a head-space element that's running parallel. Often times that's because he has a lot of narration in the film. We visit these different concepts because that's where he's going with the film. For me, I'm into it."